Thermaly expandable composition with reduced odor formation

ABSTRACT

A thermally expandable composition includes at least one polymer P cross-linkable by peroxide, and at least one acrylate, and at least one peroxide, azodicarbonamide and a zinc compound. The thermally expandable composition leads to low odor formation and low ammonia emission during and after the foaming process. The thermally expandable composition further shows excellent properties in terms of expansion stability.

TECHNICAL FIELD

The present invention relates to a thermally expandable composition,comprising at least one acrylate and at least one peroxide, as well as abaffle and/or reinforcement element for hollow structures comprisingsuch a thermally expandable composition and a process for manufacturingsuch a baffle and/or reinforcement element.

Background of the Invention

Manufactured products often contain orifices and cavities or otherhollow parts that result from the manufacturing process and/or that aredesigned into the product for various purposes, such as weightreduction. Automotive vehicles, for example, include several suchorifices and cavities throughout the vehicle, including in the vehicle'sstructural pillars and in the sheet metal of the vehicle doors. It isoften desirable to seal such orifices and cavities so as to minimisenoise, vibrations, fumes, dirt, water, humidity, and the like frompassing from one area to another within the vehicle by means of sealingmembers or baffle elements built into the orifice or cavity. Likewise,such members or elements often fulfil an additional task of reinforcingthe hollow structure of the manufactured product, e.g. automotive part,so much that it becomes more resistant to mechanical stress but stillmaintains the low weight advantage of the hollow structure.

Such elements used for sealing, baffling or reinforcing often consist ofa carrier, made of plastic, metal, or another rigid material, and one ormore layers of a thermoplastic material attached to it which is able toexpand its volume when heat or another physical or chemical form ofenergy is applied, but they can also be entirely made of expandablematerial. Using an adequate design, it is possible to insert the baffleor reinforcement element into the hollow part of the structure duringthe manufacturing process but also to leave the inner walls of thestructure still accessible (or the cavities passable) by e.g. a liquid.For example, during the manufacture process of a vehicle, the hollowparts of a metal frame can still be largely covered by anelectro-coating liquid while the baffle or reinforcement elements arealready inserted, and afterwards during a heat treatment step, theexpandable thermoplastic material of the baffle or reinforcement elementexpands to fill the cavities as intended.

The development of such baffles or reinforcement elements has led tohighly advanced systems, where the expandable material is able toincrease its volume by up to 1500% or more, forming a foam-likestructure that fills the cavities and adhering to the walls of thestructure intended to be sealed, baffled, or reinforced. Especially inautomotive manufacturing, this has led to considerable weight reductionand excellent dampening of noise or vibrations in the car body.

Currently employed thermally expandable compositions often consist ofpolymers that can be cross-linked by peroxides, such as ethylene-vinylacetate polymers, in combination with comparably small, highlyfunctional acrylates which are incorporated into the cross-linkednetwork upon curing. These compositions furthermore contain blowingagents. Under activation conditions, such as elevated temperature,curing of the cross-linkable network takes place, while simultaneouslythe blowing agent decomposes and releases gases. This leads to the abovementioned volume expansion and the formation of a stable foam which inideal cases fills the cavity as intended and adheres to its walls. Sucha system is for example disclosed in DE 10 2011 080 223 A1.

Thermally expandable compositions crosslinked by acrylates and peroxideusing azodicarbonamide as a blowing agent can have the disadvantage ofodor formation since azodicarbonamide is potential emitter of ammoniawhen exposed to higher temperature. Especially in the automotiveindustry, many manufacturers rely on the test method VDA 270 todetermine the odor of materials used and demand for low-odor materials.

It is thus desirable to obtain a thermally expandable compositioncontaining azodicarbonamide as a blowing agent that does not suffer fromthese limitations and leads to low odor formation and low ammoniaemission during and after the foaming process.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a thermallyexpandable composition that does not suffer from these limitations andleads to low odor formation and low ammonia emission during and afterthe foaming process.

Surprisingly, the present invention provides a solution to that problemby providing a thermally expandable composition, comprising

-   -   (a) at least one polymer P, cross-linkable by peroxide, and    -   (b) at least one acrylate A, and    -   (c) at least one peroxide PE, and    -   (d) azodicarbonamide ADCA,    -   (e) zinc compound ZC.    -   The molar ratio of said zinc compound ZC to said peroxide PE is        between 0.1 and 6.0, preferably between 0.1 and 4.0.    -   The molar ratio of said azodicarbonamide ADCA to said peroxide        PE is between 5 and 30, preferably between 8 and 25.

The composition according to the present invention is particularlysuitable to be used in a sealing, baffle or reinforcement element, forexample in automotive applications. Further aspects of the presentinvention are subject of other independent claims. Preferred embodimentsof the invention are subject of dependent claims.

DETAILED DESCRIPTION OF THE INVENTION

The unit term “wt.-%” means percentage by weight, based on the weight ofthe respective total composition, if not otherwise specified. The terms“weight” and “mass” are used interchangeably throughout this document.

The term “functionality” in connection with a molecule describes in thisdocument the number of chemical functional groups per molecule. The term“polyfunctional” describes a molecule with more than 1 functional groupsof a given type. For example, a polyfunctional acrylate with afunctionality of 3 describes a molecule with 3 acrylate groups. The term“average functionality” is used if a mixture of molecules is presentthat differ slightly in individual functionality, but in average exhibita given functionality, as it is sometimes the case with technical gradechemicals.

The term “equivalent” in connection with chemical functional groupsdescribes in this document the mass amount of a substance that equalsits equivalent weight. Normally, the equivalent weight is defined as theamount of substance that contains 1 mole of a defined functional group,such as an acrylate group or a peroxide function. The ordinarily skilledartisan in the field of polymer composition formulation uses suchnumbers to calculate appropriate ratios for active components, and suchvalues are commonly provided by producers of functional chemicals,especially polymers. Accordingly, the “equivalent ratio” (EQ) of twosubstances is understood herein as the ratio of the equivalents of afirst substance to the equivalents of the second substance in a givencomposition.

The term “radical” used in this document describes, as known to a personwith ordinary skill in the art of chemistry, a chemical species with anunpaired valence electron. The cross-linking reactions involved in thecuring or hardening of the polymer system of the present inventionfollow a radical mechanism.

Melt flow index (MFI) is determined by the ASTM D1238 standard method,using a capillary rheometer at 190° C. and a weight of 2.16 kg. MFIvalues describe the amount of polymer coming out of the capillary underpressure of the defined weight and at the defined temperature during agiven time.

Volume changes on the thermally expandable material are determined usingthe DIN EN ISO 1183 method of density measurement (Archimedes principle)in deionised water in combination with sample mass determined by aprecision balance.

The present invention comprises as a first necessary component at leastone polymer P that is cross-linkable by peroxide. Principally allthermoplastic polymers or thermoplastic elastomers capable ofcross-linking reactions with peroxides are suitable. The artisan skilledin the field describes polymers as “cross-linkable by peroxide” if thesepolymers contain functional groups, e.g. C—C double bonds, which releasehydrogen atoms under influence of a radical starter, e.g. a peroxide,from their backbone or side chain, such that a radical remains that isable to radically attack other polymer chains in a subsequent step,leading to a radical chain reaction cross-linking process and ultimatelyto a polymer network.

Suitable polymers P include, for example, styrene-butadiene copolymers,styrene-isoprene copolymers, ethylene-vinyl acetate copolymers,ethylene-methacrylate copolymers, ethylene-ethyl acrylate copolymers,ethylene butyl acrylate copolymers, ethylene-(meth)acrylic acidcopolymers, ethylene-2-ethylhexyl acrylate copolymers, ethylene-acrylicester copolymers, polyolefinc block copolymers, and polyolefins such aspolyethylene or polypropylene.

The copolymers, meaning polymers made from more than one type ofmonomer, can be block type copolymers or random copolymers.

Polymers P can also be further functionalised, meaning they can containfurther functional groups such as hydroxyl, carboxy, anhydride,acrylate, and/or glycidylmethacrylate groups.

Preferred for the present invention is one or more polymer P with anaverage melt flow index (MFI) of between 1 and 200 g/10 min, preferablybetween 10 and 100 g/10 min, more preferably between 25 and 75 g/10 min,most preferably between 35 and 55 g/10 min.

The polymer P preferably comprises ethylene-vinyl acetate (EVA). Morepreferably more than 70 wt-%, more than 80 wt-%, more than 90 wt-%, morethan 95 wt-%, more than 99 wt-%, of the Polymer P consists ofethylene-vinyl acetate (EVA), based on the total amount of the PolymerP.

In this case, the content of vinyl acetate monomers in EVA should bebetween 8 and 45 wt.-%, preferably between 15 and 30 wt.-%, based on thetotal weight of the EVA polymer.

In cases where more than one type of polymer is used, the individual MFIcombine to an average MFI of the used polymer mixture, which has to bedetermined according to ASTM D1238.

The thermally expandable composition according to the present inventionpreferably contains said at least one polymer P with an amount ofbetween 30 and 80 wt.-%, preferably between 40 and 70 wt.-%, morepreferably between 40 and 60 wt.-%, based on the weight of the totalcomposition.

In a preferred embodiment, more than one type of polymer is used aspolymer P. It was found to be beneficial for the properties of theinventive composition to use at least two types of polymer (herein namedP1 and P2) with different melt flow index (MFI), one much higher thanthe other. For example, an especially preferred embodiment uses a firstpolymer P1 with an MFI of between 100 and 200 g/10 min and a secondpolymer P2 with an MFI of between 0.1 and 60 g/10 min, preferablybetween 0.1 and 10 g/10 min, preferably with a weight ratio of the twopolymers P1:P2 in the composition of 0.7 to 1.3, preferably 0.8 to 1.2.

Preferred EVA polymers include, e.g., Elvax® 150, Elvax® 240A, Elvax®260A, Elvax® 420A (all by DuPont), or the corresponding Evatane®copolymers (by Arkema).

A second necessary component of the thermally expandable compositionaccording to the present invention is at least one acrylate A,

Preferably, the acrylate A is present with an amount of between 0.1 and5 wt.-%, preferably between 0.2 and 2 wt.-%, more preferably between 0.3and 0.75 wt.-%, based on the total weight of the composition.

Acrylate A preferably has a molecular weight of less than 2,500 g/mol,more preferably less than 1,000 g/mol.

Acrylate A preferably exhibits an acrylate functionality of at least 2or 3, preferably between 2 and 6, more preferably between 3 and 5, mostpreferably 5. More preferably, the acrylate A comprises a polyfunctionalacrylate with an acrylate functionality of at least 2 or 3, preferablybetween 2 and 6, more preferably between 3 and 5, most preferably 5, inan amount of more than 70 wt-%, more than 80 wt-%, more than 90 wt-%,more than 95 wt-%, more than 99 wt-%, based on the total amount of theAcrylate A.

Although polymer P (described above) can comprise acrylate functions, itis beneficial for the inventive composition that these two componentsare not the same chemical compound. In comparison, acrylate A isgenerally smaller than polymer P in terms of molecular weight and actsas cross-linker for polymer P also. Only using one of the two componentswould either lead to poor mechanical properties in the final product orwould inhibit the formation of a stable foam structure during and afterexpansion.

Preferred acrylates A with a functionality of 2 include ethylene glycoldimethacrylate, diethylene glycol dimethacrylate, triethylene glycoldimethacrylate, triethylene glycol diacrylate, tripropylene glycoldimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanedioldimethacrylate, 1,10-dodecanediol dimethacrylate, 1,6-hexandieoldimethacrylate, neopentylglycol dimethacrylate, and polybutylene glycoldimethacrylate.

Preferred acrylates A with a functionality of 3 or higher includeglycerol triacrylate, pentaerythritol triacrylate, pentaerythritoltrimethacrylate, trimethylolpropane triacrylate, trimethylolpropanetrimethacrylate, tetramethylolmethane tetraacrylate,Di-(trimethylolpropane) tetraacrylate, pentraerythritol tetraacrylate,dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate,tri(2-methacryloxyethyl) trimellitate, tri(2-acryloxyethyl)isocyanurate, as well as their ethoxylated or propoxylated derivates.

Especially preferred acrylates A exhibit a functionality of 5, such asdipentaerythritol pentaacrylate.

Further preferred acrylates include highly functional, hyperbranchedacrylates with functionalities of between 6 and 16, or higher. Examplesof such preferred acrylates include hyperbranchedpolyester-polyacrylates, for example Sartomer® CN2303 and Sartomer®CN2305, both by Arkema.

A third necessary component of the thermally expandable compositionaccording to the present invention is at least one peroxide PE.

The thermally expandable composition according to the present inventionpreferably contains said peroxide PE in an amount of between 2.5 and 5wt.-%, preferably between 2.8 and 4.8 wt.-%, based on the total weightof the composition.

It is advantageous for the inventive composition to use a peroxide thatis essentially inert at room temperature (23° C.) and exhibits anactivation temperature suitable for the intended purpose. For example,if the composition is used for a baffle and/or reinforcement element inautomotive manufacturing, an activation temperature of between 130 and250° C. is preferred. Furthermore, it is advisable to select a peroxidewith an activation temperature compatible with the decompositiontemperature of the azodicarbonamide ADCA. If those two temperaturesdiffer too much, it may be more difficult to obtain a thermallyexpandable composition with optimal performance and stability. Apartfrom that, other, at room temperature solid components (such as in somecases polymer P) have to be compatible with these components as well,for example in terms of softening or melting point.

Preferred peroxides for the inventive composition are organic peroxides,such as keton peroxides, diacyl peroxides, peresters, perketals, andhydroperoxides. Examples of such preferred peroxides include cumenehydroperoxide, t-butyl peroxide, bis(t-butylperoxy)-diisopropyl benzene,di(t-butylperoxy isopropyl) benzene, dicumyl peroxide, t-butylperoxybenzoate, di-alkylperoxy dicarbonate, diperoxyketals (such as1,1-di-t-butylperoxy-3,3,5-trimethyl cyclohexane), keton peroxides (suchas methyl ethyl keton peroxide), and 4,4-di-t-butylperoxy-n-butylvalerate.

Especially preferred are 3,3,5,7,7-pentamethyl-1,2,4-trioxepane,2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne, di-t-butyl peroxide,2,5-dimethyl-2,5-di(t-butylperoxy) hexane, t-butyl cumyl peroxide,di(t-butylperoxy isopropyl) benzene, dicumyl peroxide,butyl-4,4-di(t-butylperoxy) valerate, t-butylperoxy-2-ethylhexylcarbonate, 1,1-di(t-butylperoxy)-3,3,5-trimethyl cyclohexane,t-butylperoxy benzoate, di(4-methylbenzoyl) peroxide, and dibenzoylperoxide.

Most preferred peroxides for the present inventive composition includedicumyl peroxide, available for example under the trade names Perkadox®BC-40B-PD by Akzo Nobel or Peroxan® DC-40 PK by Pergan and/ordi(t-butylperoxyisopropyl) benzene, available for example under thetrade names Perkadox® 14-40B-PD by Akzo Nobel or Peroxan® BIB-40 P byPergan, wherein di(t-butylperoxyisopropyl) benzene is especiallypreferred.

It may be advantageous for the present invention to use peroxide that isimmobilised on a support material, such as silica, kaolin, and/orcalcium carbonate, or other suitable materials. This approach mayfacilitate handling, dosage, and evenly distribution of the peroxide inthe composition. Examples for such immobilised peroxide includePerkadox® BC-40B-PD by Akzo Nobel (40 wt.-% dicumyl peroxide on calciumcarbonate) or Perkadox® 14-40K-PD by Akzo Nobel (40 wt.-%di(t-butylperoxyisopropyl) benzene on clay and silica). However, carehas to be taken in such cases to correctly calculate the wt.-% andespecially the equivalents of active substance in the composition, as inthis document these values always refer to active compound, and do notinclude possibly present support material.

The fourth essential component of the present inventive composition isazodicarbonamide ADCA. Azodicarbonamide ADCA is a blowing agent thatdecomposes under influence of temperature and causes an expansion in thethermally expandable composition.

Preferably, the azodicarbonamide is included in the present inventivecomposition with an amount of between 1 and 15 wt.-%, preferably between5 and 10 wt.-%, more preferably between 7 and 9.5 wt.-%, based on thetotal weight of the composition.

The heat required for the decomposition reaction that causes the foaming(expansion) can be applied externally or internally, the latter e.g.from an exothermic reaction.

If the present inventive thermally expandable composition finds a use ina baffle and/or reinforcement element, e.g. in automotive manufacturing,it is preferable that the activation temperature of the azodicarbonamideis in line with the manufacturing conditions of the automotive part tobe baffled or reinforced. As an example, the baffle and/or reinforcementelement can be inserted into a cavity of a structure that needs to betreated by an electrocoating liquid, in its unexpanded state stillleaving the surface of the structure accessible, and subsequently,during the heat treatment of the automotive part (i.e. the curingprocedure for the electrocoating liquid), the baffle and/orreinforcement element simultaneously (or shortly thereafter) expands toits intended final shape and at least partially closes or fills thecavity. In such a case, the expansion temperature should correspond tothe temperature conditions of said heat treatment, i.e. to between 90°C. and 200° C.

Accordingly, it is advisable to select the peroxide used in theinventive composition in such a way that its activation temperature isin the same range, or slightly below the decomposition temperature ofthe azodicarbonamide. This ensures that the radical mechanisms leadingto polymer cross-linking take place at a point which enables theformation of a stable, foam-like structure.

The molar ratio of the zinc compound ZC to the peroxide PE is between0.1 and 6.0, preferably between 0.1 and 4.0

Compositions with a molar ratio of less than 0.1 suffer from low foamexpansion at 180° C. and high odor formation. This can be seen forexample in the comparison of examples Ex2 to Ex4 with the examples Ex5to Ex9.

Compositions with a molar ratio of more than 6.0 suffer from high odorformation as well as high ammonia emission. This can be seen for examplein the comparison of example Ex9 with the examples Ex5 to Ex8.

It might be beneficial if the molar ratio of the zinc compound ZC to theperoxide PE is between 0.1 and 4.0, 0.1 and 3.0, 0.1 and 2.5, 0.2 and2.0, 0.5 and 2.0, 0.8 and 2.0, preferably between 0.8 and 1.5.

Such a molar ratio is advantageous for low odor formation. This can beseen for example in the comparison of examples Ex4 to Ex9.

It can also be beneficial if the molar ratio of the zinc compound ZC tothe peroxide PE is between 0.1 and 6.0, 0.2 and 6.0, 0.5 and 6.0, 0.8and 6.0, 1.5 and 6.0, preferably between 2.0 and 6.0. This brings theadvantage of highly expanded foams at 180° C. This can be seen forexample in the comparison of examples Ex4 to Ex9.

It might be further beneficial if the molar ratio of the zinc compoundZC to the peroxide PE is between 0.5 and 2.5, 0.5 and 2.0, 0.5 and 1.5,preferably between 0.8 and 1.5.

This is advantageous for obtaining highly expanded foams at 180° C. andat the same time at 200° C. as well. This can be seen for example in thecomparison of examples Ex6 to Ex8.

It can also be an advantage if the molar ratio of the zinc compound ZCto the peroxide PE is between 0.1 and 2.0, preferably between 0.2 and1.5. Such a molar ratio is advantageous for low ammonia emission. Thiscan be seen for example in the comparison of examples Ex4 to Ex9.

The molar ratio of the azodicarbonamide ADCA to the peroxide PE isbetween 5 and 30, preferably between 8 and 25.

Compositions with a molar ratio of less than 5 suffer from low foamexpansion. Compositions with a molar ratio of more than 30 suffer fromhigh odor formation as well as high ammonia emission. This can be seenfor example in the comparison of example Ex1 with the examples Ex5 toEx8.

It might be beneficial if the molar ratio of azodicarbonamide ADCA toperoxide PE is between 8 and 25, 12 and 25, preferably between 6 and 25.Such a molar ratio is advantageous for obtaining highly expanded foamsat 200° C. This can be seen for example in the comparison of examplesEx10 to Ex12 as well as in the comparison with Ex8 and Ex12 and Ex7 andEx11.

It might be further beneficial if the molar ratio of azodicarbonamideADCA to peroxide PE is between 8 and 25, 12 and 25, 16 and 25,preferably between 20 and 25. Such a molar ratio brings the advantage ofobtaining highly expanded foams at 160° C. and 180° C. This can be seenfor example in the comparison of examples Ex10 to Ex12.

It can also be an advantage if the molar ratio of azodicarbonamide ADCAto peroxide PE is between 8 and 25, 12 and 25, 16 and 25, preferablybetween 20 and 25. This is advantageous for obtaining highly expandedfoams at 160° C. and 180° C. and at the same time at 200° C. as well.This can be seen for example in the comparison of examples Ex10 to Ex12.

The fifth essential component of the present inventive composition is atleast one zinc compound ZC.

It is advantageous if the zinc compound ZC is selected from the groupconsisting of zinc oxide, zinc stearate, zinc bis(p-toluenesulphinate)and zinc bis(benzenesulphinate), most preferred zinc oxide.

The inventive thermally expandable composition preferably comprises suchzinc compound ZC as an activator for the azodicarbonamide with an amountof between 0.25 and 5 wt.-%, preferably between 0.25 and 3.5 wt.-%, morepreferably between 0.3 and 2 wt.-%, based on the total weight of thecomposition.

It might be beneficial if the molar ratio of the azodicarbonamide ADCAto the sum of peroxide PE and zinc compound ZC (ADCA: (PE+ZC)) isbetween 2 and 20, 3 and 15, 4 and 12, preferably between 5 and 12.

Compositions with a molar ratio of more than 20 have a high odorformation as well as a high ammonia emission.

Compositions with a molar ratio of less than 2 have low expansion rates.

The inventive thermally expandable composition preferably has a molarratio of said zinc compound ZC to peroxide PE between 0.25 and 2,preferably between 0.3 and 1.8. This is advantageous for highly expandedfoams. This can be seen for example in the comparison of examples E3, E8and E9.

It might be further preferable if the molar ratio of the zinc compoundZC to the peroxide PE is between 0.3 and 1.8, 0.5 and 1.8, 0.8 and 1.8,0.8 and 1.5, preferably between 0.8 and 1.2. Such a molar ratio isadvantageous for highly expanded foams, especially at temperatures 155°C. and 160° C. This can be seen for example in the comparison ofexamples E3, E8 and E9.

Another preferable molar ratio of the zinc compound ZC to the peroxidePE is between 0.3 and 1.8, 0.3 and 1.6, 0.3 and 1.5, 0.3 and 1.2, 0.3and 1.0, 0.3 and 0.8, preferably between 0.4 and 0.6. Such compositionshave the benefit of highly expanded foams, especially at temperatures180° C. and 200° C. This may be seen by the comparison of examples E3,E8 and E9.

Apart from the essential ingredients, the present inventive thermallyexpandable composition may contain other components commonly used insuch compositions and known to the ordinarily skilled artisan in thefield. These include, for example, fillers, colorants, dispersion aidsor homogenizers, adhesion promoters, antioxidants, stabilizers, and thelike.

Suitable as fillers are, e.g., ground or precipitated calcium carbonate,calcium-magnesium carbonate, talcum, gypsum, graphite, barite, silica,silicates, mica, wollastonite, carbon black, or the mixtures thereof, orthe like.

Fillers are, if at all, preferably incorporated in the inventivecompositions with an amount of between 1 and 15 wt.-%, based on thetotal weight of the composition.

Colorants or dyes, such as pigments, e.g. on the basis of carbon black,may be included in the present inventive compositions. Their amount ispreferably between 0 and 1 wt.-%, based on the total weight of thecomposition.

Dispersion aids or homogenizers, sometimes described as wetting agentsor surface-active agents, may be beneficial for the present inventivecomposition in order to facilitate a homogeneously mixed composition.Preferably used such compounds include hydrocarbon resins, for exampleNovares® TL 90 available from Rutgers, Germany, Wingtack® resins (byCray Valley), Escorez® tackifying resins (e.g., Escorez® 1304, byExxonMobil), and Piccotac® hydrocarbon resins (e.g., Piccotac® 1100 orPiccotac® 1100E, by Eastman). Such compounds are preferably included inthe inventive compositions with an amount of between 2 and 10 wt.-%,preferably between 4 and 8 wt.-%, more preferably between 5 and 7 wt.-%,based on the total weight of the composition.

In preferred embodiments, the inventive composition also includesadhesion promoters. Preferably these substances are incorporated intothe polymer network during the cross-linking reactions via functionalgroups similar to those present in polymer P. Suitable adhesionpromoters include, for example, ethylene-glycidyl methacrylatecopolymers, such as Lotader® ADX 1200S, Lotader® AX8840, Lotader® 3210,Lotader® 3410 (by Arkema) or Lotryl® copolymers (by Arkema).

Adhesion promoters are preferably used in compositions according to thepresent invention with an amount of between 2 and 15 wt.-%, preferablybetween between 4 and 10 wt.-%, more preferably between 5 and 7 wt.-%,based on the total weight of the composition.

Further potentially useful additives include antioxidants andstabilizers, commonly used in polymer-based compositions and known tothe person skilled in the art of polymer-based composition formulation.Examples of suitable antioxidants and stabilizers include stericallyhindered thioethers, sterically hindered aromatic amines, and/orsterically hindered phenols, such asbis(3,3-bis(4′-hydroxy-3-t-butylphenyl)butanoic acid) glycol ester. Suchsubstances are preferably included with an amount of between 0 and 0.5wt.-%, preferably between 0.1 and 0.3 wt.-%, based on the total weightof the composition.

The compositions according to the present inventions can be manufacturedby mixing the components in any suitable mixing apparatus, e.g. in adispersion mixer, planetary mixer, twin mixer, continuous mixer,extruder, or dual screw extruder.

It may be advantageous to heat the components before or during mixing,either by applying external heat sources or by friction generated by themixing process itself, in order to facilitate processing of thecomponents into a homogeneous mixture by decreasing viscosities and/ormelting of individual components. However, care has to be taken, e.g. bytemperature monitoring and use of cooling devices where appropriate, notto exceed the activation temperatures of the azodicarbonamide and/orperoxide. The final composition is preferably essentially solid at roomtemperature (23° C.), meaning that it does not visibly deform at thistemperature just by means of gravity during at least 24 h.

After mixing, the resulting composition may be shaped into its desiredform by, e.g., extruding, blow-moulding, pelleting, injection moulding,compression moulding, punching or stamping or any other suitableprocess.

The thermally expandable compositions may be produced in a substantiallyone-step process, involving the addition of all components in a seriesand/or simultaneously. However, it may also be advantageous to formulatethe composition as a two-part system, or even multipart system, and mixthese parts into the final composition at a later stage. Such anapproach may, for example, increase shelf life of the composition inplaces with demanding conditions (such as extraordinarily hightemperatures), optimise storage room demand and transport weight, andallow for tailor-made, modular compositions regarding differentapplications.

The expansion of the thermally expandable composition according to thepresent invention is triggered by heat. This means, both theazodicarbonamide and the peroxide component are activated by a thermalprocess that exceeds their respective activation temperature andexhibits a duration long enough for both processes (peroxide-initiatedradical polymerisation and decomposition of the azodicarbonamideincluding gas formation) to proceed until the expandable material hasexpanded and cured into its intended final (sufficiently expanded andstable) state. The optimal temperature and duration (dwell time) dependson the azodicarbonamide and peroxide used in the inventive composition.These values are provided by the manufacturers of such components and/orare known to the ordinarily skilled artisan. Commonly, such activationtemperatures are in the range of 130° C. to 250° C., preferably 150° C.to 200° C., and require a dwell time of between 10 and 90 min,preferably between 15 and 60 min.

Another aspect of the present invention is the use of such thermallyexpandable compositions for the manufacturing of baffle and/orreinforcement elements. Such elements are used to seal, baffle, and/orreinforce hollow structures, e.g. a cavity in a hollow structural partof an automobile. Hollow parts in cars may include body components(e.g., panels), frame components (e.g., hydroformed tubes), pillarstructures (e.g., A, B, C, or D-pillars), bumpers, roofs, or the like.

With regard to activation of the thermally expandable compositionaccording to the present invention when used in automotivemanufacturing, it is advantageous to couple the thermal activation ofthe composition with another process step involving heat treatment. Anexample for such a process step is electrocoating (cathodic dippainting/coating) of the chassis or car body.

In one preferred embodiment, such a baffle and/or reinforcement elementfor hollow structures consists essentially of a thermally expandablecomposition. In this case, it is advantageous to design the shape of theelement in a way that it can be easily fitted into and attached to thewalls of the hollow structure to be baffled and/or reinforced.Manufacturing is in this case preferably done by injection moulding,punching or stamping, or extrusion through a shape template.

In another preferred embodiment, such a baffle and/or reinforcementelement for hollow structures comprises, apart from the thermallyexpandable composition, a carrier element on which the inventivethermally expandable composition is deposited or attached. Such a designmay be more cost-efficient and it may facilitate fixation of the baffleand/or reinforcement element on the walls of the structure to be baffledand/or reinforced, e.g. by incorporation of pins, bolts, or hooks on thecarrier element. Furthermore, with a suitable design of the carrierelement, the mechanical performance and stability of the baffle and/orreinforcement element according to the present invention can beincreased.

Said carrier element may consist of any material that can be processedinto a shape useable for an embodiment of the present invention.Preferred materials are polymeric materials, such as a plastic,elastomers, thermoplastics, thermosettable polymers, a blend or othercombination thereof, or the like. Preferred thermoplastic materialsinclude, without limitation, polymers such as polyurethanes, polyamides,polyesters, polyolefins, polysulfones, poly(ethylene terephthalates),polyvinylchlorides, chlorinated polyolefins, or the like. Especiallypreferred are high-temperature stable polymers such as poly(phenylethers), polysulfones, polyethersulfones, polyamides, preferablypolyamide 6, polyamide 6,6, polyamide 11, polyamide 12, or a mixturethereof. Other suitable materials include metals, especially aluminiumor steel, or naturally grown, organic materials, such as wood or other(pressed) fibrous materials. Also glassy or ceramic materials can beused. It is possible to use any combination of such materials. It isalso contemplated that such materials can be filled (e.g. with fibres,minerals, clays, silicates, carbonates, combinations thereof or thelike) or foamed.

The carrier element can further exhibit any shape or geometry. It canalso consist of several, not directly connected parts. For example, itcan be massive, hollow, or foamed, or it can exhibit a grid-likestructure. The surface of the carrier element can typically be smooth,rough, or structured, according to the intended use of the baffle and/orreinforcement element.

The manufacturing process of a baffle and/or reinforcement element inaccordance with the present invention depends largely on the material ofthe carrier element. If the material of the carrier element can be(injection-) moulded or extruded, the whole baffle and/or reinforcementelement can be produced in a two-step injection-moulding process or aco-extrusion process of the carrier element and the thermally expandablecomposition. If using a two-step injection moulding process, in a firststep, material for the carrier element is injected into the mould. Aftersolidification, the cavity of the injection moulding tool is enlarged oradjusted, or the injection-moulded piece is transferred into anothertool and the second component, in this case the material for thethermally expandable composition, is injected.

If the carrier element is not shaped by injection-moulding or extrusion,e.g., because it consist of a metal or alloy, it may be firstmanufactured by a suitable process and then introduced into theinjection-moulding tool, and the thermally expandable composition may beinjection-moulded into the tool where the carrier element was placed.Another possibility is to extrude the thermally expandable compositiononto the pre-fabricated carrier element. Of course there is also thepossibility of manufacturing the carrier element and the expandablecomposition element individually by a suitable process, and thenattaching the expandable composition element to the carrier element byany suitable means, such as chemically or physically, e.g. by gluing orthe like, or mechanically, e.g. by bolting, screwing, or the like.

Another aspect of the present invention is the use of the baffle and/orreinforcement element as described above to seal, baffle, or reinforce acavity or hollow structure of a land-, water-, or air-vehicle,preferably an automotive vehicle, and/or a cavity of a building suchthat the transmission of noise, vibrations, humidity, and/or heat isreduced, and/or the object surrounding said cavity is mechanicallystrengthened.

A further aspect of the present invention is a method for sealing,baffling and/or reinforcing a cavity or hollow structure, characterisedin that an element comprising a thermally expandable compositionaccording as described above is introduced into said cavity or hollowstructure and subsequently thermally expanded such that said cavity orhollow structure is at least partially filled by the expandedcomposition. Preferred temperature for the thermal expansion process isbetween 130° C. and 250° C.

The invention is further explained in the following experimental partwhich, however, shall not be construed as limiting the scope of theinvention.

Examples 1. Formulation of Example Compositions 1.1 Compositions

The compositions Ex1-Ex12 were prepared according to the procedure shownbelow. The exact individual compositions in wt.-%, based on the totalweight of the individual respective composition, are listed in Table 2.

Details on the ingredients used in the compositions Ex1-Ex12 describedherein are listed in Table 1.

TABLE 1 Details on the ingredients and their trade names used in theinventive and non-inventive example compositions in this document.Ingredient Description Properties or trade name Polymer P1Ethylene-vinyl acetate (EVA) EVA with 18 wt.-% vinyl acetate copolymerresin monomer and a melt flow index (MFI) of 150 g/10 min (ATSM D1238)Polymer P2 Ethylene-vinyl acetate (EVA) EVA with 28 wt.-% vinyl acetatecopolymer resin monomer and a MFI of 6 g/10 min (ATSM D1238) AdhesionEthylene-glycidyl methacrylate MFI of 5 g/10 min (ASTM D1238) promotercopolymer (8 wt.-% glycidyl methacrylate) Tackifier C5-C9-Hydrocarbonresin Mn 1100 g/mol, Mw 2000 g/mol, Dispersion Polyethylene wax Meltingpoint 118° C. (ASTM aid D3954) Stabilizer Stabilizer Irganox 1010 FillerCalcium carbonate ZnO Zinc oxide, Activator Sigma Aldrich, SwitzerlandACDA Azodicarbonamide Tramaco, Germany PE Peroxide, Di-(2-tert.-butyl-Pergan, Germany peroxyisopropyl)-benzene (40 wt.-%) on calcium carbonateand silica Acrylate Dipentaerythritol pentaacrylate Sartomer Arkema

1.2 Mixing and Moulding Procedure

All inventive and non-inventive example compositions in this documentwere prepared according to the following procedure:

In a first step, polymer P1 and polymer P2, the adhesion promoter, andthe dispersion aid were mixed and melted at 95° C. with a mixing rate of50 rpm (rounds per minute) during 10 min (minutes). After this, half ofthe activator amount was added during 1 min and mixing was continuedduring 4 min at 50 rpm. Mixing was continued at 20 rpm during 5 minuntil the mixture cooled down to 95° C.

After this, the azodicarbonamide, acrylate, and the second half of theactivator amount were added during 1 min, followed by mixing at 50 rpmfor 1 min. Finally the peroxide and all the rest were added during 1 minand mixing was continued for 2 min at 50 rpm.

The mixtures were moulded with a temperature of 90° C. and a pressure of60 bar during 15 s (seconds) into test shapes with a dimension of25×25×3 mm (millimetres). These test shapes were cooled down to roomtemperature (23° C.) and used for the subsequently described expansiontest experiments.

2 Testing of Example Compositions 2.1 Expansion Stability

Expansion stability was tested in all samples by heat treatment of theindividual samples at various temperatures during 30 min in an oven. Thetemperatures and magnitude of expansion (in % based on the originalvolume prior to expansion) at the corresponding temperatures are shownin Table 2.

Expansions were quantified for each sample by measuring the densitybefore and after expansion. The densities were determined according toDIN EN ISO 1183 using the water immersion method (Archimedes principle)in deionised water and a precision balance to measure the mass.

The expansion stability can be estimated by comparing the expansion of asample at different temperatures. Table 2 lists the expansions of thecomposition samples at 155° C., 160° C., 180° C., and 200° C.

Table 2 furthermore show the molar ratio of the zinc compounds ZC to theperoxide PE “(ZnO:PE)”, the molar ratio of azodicarbonamide ADCA toperoxide PE “(ADCA:PE)” and molar ratio of the azodicarbonamide ADCA tothe sum of peroxide PE and zinc compound ZC (ADCA:(PE+ZnO)).

2.2 Odor Test VDA 270

This odor test was performed according to the VDA 270 “Determination ofthe odor behavior of automotive interior materials” in line with the VDA“Verband der Automobilindustrie” on February 2017. The VDA 270 is forexample used by various OEMs, such as Daimler Chrysler, BMW and Porsche.The rating system ranges from Grade 1 “imperceptible” to Grade 6“unbearable”. Square specimens (plaque) with an edge length of 0.4 cmwere expanded for 30 min in an oven at 180° C. giving rise to a volumeof 50 ccm. The expanded sample was then put into a 1000 ccm containerfor further analysis.

Ammonia

This odor test was performed by assessing the smell of the foamedsamples and rated n=no smell of ammonia, w=weak smell of ammonia,y=strong smell of ammonia, yy=very strong smell of ammonia.

TABLE 2 Ingredients Mw wt.-% Ex1 Ex2 Ex3 Ex4 Ex5 Ex6 Ex7 Ex8 Ex9 Ex10Ex11 Ex12 P1 [%] 30.66 31.87 32.24 31.13 31.10 31.05 30.98 30.82 29.9831.11 31.32 31.50 P2 [%] 17.88 18.58 18.80 18.15 18.13 18.11 18.06 17.9717.48 18.15 18.26 18.38 Adhesion [%] 14.24 14.80 14.98 14.46 14.44 14.4214.39 14.31 13.93 14.46 14.55 14.64 promotor Tackifier [%] 6.08 6.326.40 6.17 6.17 6.16 6.14 6.11 5.95 6.17 6.21 6.25 ZnO 81.38 [%] 3.770.10 0.26 0.51 1.02 3.69 0.51 0.52 0.52 Dispersion aid [%] 5.52 5.745.81 5.61 5.60 5.59 5.58 5.55 5.40 5.61 5.64 5.68 Stabilizer [%] 0.610.63 0.64 0.62 0.62 0.62 0.61 0.61 0.59 0.62 0.62 0.63 Filler [%] 10.1410.53 10.66 10.29 10.28 10.26 10.24 10.19 9.91 10.29 10.35 10.42 ACDA116.08 [%] 8.27 8.60 8.70 8.40 8.39 8.38 8.35 8.31 8.09 8.40 8.45 8.50PE 338.48 [%] 2.28 2.36 1.19 4.61 4.61 4.60 4.59 4.56 4.44 4.12 3.522.92 Acrylate [%] 0.55 0.57 0.58 0.56 0.56 0.55 0.55 0.55 0.54 0.56 0.560.56 TOTAL [%] 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00100.00 100.00 100.00 100.00 RESULTS Expansion 30′ [%] n.d. n.d. n.d.n.d. n.d. 1356 1740 1937 n.d. 1862 n.d. 2138 160° C. Expansion 30′ [%]2303 607 560 719 1310 1908 1934 2073 2270 1875 2210 2308 180° C.Expansion 30′ [%] n.d. n.d. n.d. n.d. n.d. 1447 1321 968 n.d. 881 14251402 200° C. Odor test Rating [R] 4 4.33 5 4.33 4 3.8 3.1 3.4 5 3.4 3.13.7 Ammonia [R] y y yy n n n.d. n w y n n w Molar ratio 17.2 0.0 0.0 0.00.2 0.6 1.2 2.3 8.6 1.3 1.5 1.9 (ZnO:PE) Molar ratio 26.5 26.6 53.3 13.313.3 13.3 13.3 13.3 13.3 14.9 17.5 21.2 (ADCA:PE) Molar ratio 1.5 26.653.3 13.3 10.8 8.4 6.2 4.0 1.4 6.5 6.9 7.4 ADCA:(PE + ZnO) n.d. = notdetermined

1. A thermally expandable composition, comprising (a) at least onepolymer P, cross-linkable by peroxide, and (b) at least one acrylate A,and (c) at least one peroxide PE, and (d) azodicarbonamide ADCA, (e)zinc compound ZC, wherein the molar ratio of the zinc compounds ZC tothe peroxide PE is between 0.1 and 6.0, and the molar ratio of theazodicarbonamide ADCA to the peroxide PE is between 5 and
 30. 2. Thethermally expandable composition according to claim 1, wherein the molarratio of the zinc compound ZC to the peroxide PE is between 0.1 and 4.0.3. The thermally expandable composition according to claim 1, whereinthe molar ratio of the zinc compound ZC to the peroxide PE is between0.5 and 2.5.
 4. The thermally expandable composition according to claim1, wherein the molar ratio of the zinc compound ZC to the peroxide PE isbetween 0.1 and 2.0
 5. The thermally expandable composition of claim 1,wherein the molar ratio of the azodicarbonamide ADCA to the peroxide PEis between 8 and
 25. 6. The thermally expandable composition of claim 1,wherein the molar ratio of the azodicarbonamide ADCA to the peroxide PEis between 12 and
 25. 7. The thermally expandable composition of claim1, wherein the molar ratio of the azodicarbonamide ADCA to the sum ofperoxide PE and zinc compound ZC (ADCA:(PE+ZC)) is between 2 and
 20. 8.The thermally expandable composition of claim 1, wherein the zinccompound ZC is selected from at least one of the group consisting ofzinc oxide, zinc stearate, zinc bis(p-toluenesulphinate) and zincbis(benzenesulphinate).
 9. The thermally expandable composition of claim1, wherein the polymer P comprises ethylene-vinyl acetate (EVA), andmore than 80 wt-%, of the Polymer P consists of ethylene-vinyl acetate(EVA), based on the total amount of the Polymer P.
 10. The thermallyexpandable composition of claim 1, wherein the acrylate A comprises apolyfunctional acrylate with an acrylate functionality of at least 2 or3, in an amount of more than 70 wt-%, based on the total amount of theAcrylate A.
 11. A baffle and/or reinforcement element for hollowstructures, wherein the element comprises a thermally expandablecomposition according to claim
 1. 12. A method comprising sealing,baffling, or reinforcing a cavity or hollow structure of a land-,water-, or air-vehicle, and/or a cavity of a building with the baffleand/or reinforcement element according to claim 11, such that thetransmission of noise, vibrations, humidity, and/or heat is reduced,and/or the object surrounding the cavity is mechanically strengthened.13. A method for sealing, baffling and/or reinforcing a cavity or hollowstructure, wherein an element comprising a thermally expandablecomposition according to claim 1 is introduced into the cavity or hollowstructure and subsequently thermally expanded such that the cavity orhollow structure is at least partially filled by the expandedcomposition.